Hi, I'm wondering why there are not many manufactures of factory made polyurethane foam SIP's? With the higher "R" values, they seem like a good idea. Am I missing something? FWIW, the search engine doesn't seem to be working.

Posted By Boyne on 11 Mar 2014 04:15 PM
Hi, I wondering why there are not many manufactures of factory made polyurethane foam SIP's? With the higher "R" values, they seem like a good idea. Am I missing something? FWIW, the search engine doesn't seem to be working.

It offgasses, shrinks and looses R value with age
and for those that need to work with it......... need to wear a mask when cutting it, the dust is an irritant to the eyes and skin

To expand on that answer, all materials have pros and cons. The accuracy of the list depends on who you ask.
PU foam is a great core for SIPs. It will deliver a relatively high r-value. The term "aged r-value" is used to describe the gradual loss of blowing agent in the cell structure. This loss over time is replaced by air (which has a lower r-value). Hence, the aged r-value of PU is slightly above 6 per inch. If you ask a PU salesman, he may be inclined to tout the newly injected foam having an r-value as high as 8. This loss of blowing agent in the world of foam insulation is called "off-gassing".
The well informed builder and consumer know that air-tightness is as important if not more important than r-value. Therefore, a larger panel with properly sealed joints will always deliver better performance than a high r-value assembly that is improperly installed.
The PU panel is mostly available in 4 foot widths and this leads to more joints (with the increase in labor and joints)
More importantly, the PU panel has a maximum thickness due to the limitations of the modern blowing agents used. This means the limitation in thickness creates a lower span capability. When looking at a long span, a PU supplier might recommend adding lumber or steel in the joint to bolster the capacity of the panel. However, anything other than foam in a panel joint is harder to seal, takes longer to install and creates a thermal bridge.
This is why good SIP designers look for a panel thickness that will meet the needs of the span without supplemental spline material. Let the panel do ALL the work!
PU tends to cost more per square foot than either XPS or EPS.
The manufacturing process of PU requires a higher capital expenditure and a higher degree of "babysitting". Get the ratios, pressure, temperature, humidity, density, or chemistry wrong and you can have a real problem. In fact, the problem may not be immediately apparent and could cause shrinkage after the panel is made. To be fair, I've seen shrinkage in both EPS and XPS as well, but for different reasons, and it's very uncommon.
On the environmental side, PU has chemistry that is not viewed favorably in some areas. However, both XPS and EPS have similar yet slightly different environmental issues.
From and installers perspective, PU is the hardest to modify and fabricate in the field. PU is a thermoset material and can not be modified with hot wires and the like to create chases, reliefs, etc. All fabrication most be done with brush, blade, or bit which creates dust and may require special equipment that is not readily available to the one-time SIP installer.

That's my short answer.

Al

acobb,

I assume that you were talking about PU SIPs with OSB cores when you mentioned adding lumber or steel to increase span.   Correct?  Do you happen to know the maximum thickness of PU panels with OSB skins?  I have used only metal skin PU SIPs so I am not that familiar with OSB SIPs.

Some metal skin PU SIP companies produce a panel with profiles that enhance their strength.   Some increase strength by using thicker metal skins.  I suppose that OSB SIPs would gain strength if the skins were thicker.  Is that correct?

The timber frame company I'm planning to build my home uses a SIP company called Thermocore. Their web site says the panels can be up to 8' x 24'. Available in 4", 6", and 8" thickness. I'm planning 6" walls at R-40 and 8" roof at R-50. The timber frame company will erect both the frame and SIP's. Electrical junction boxes are installed at the factory before foaming. At installation, the builder drills hole through bottom plate and provides 3/4" conduit from junction box to basement. More initial planning, but should make for quicker electrical install. Thoughts or comments welcome.

What kind of roof design are you planning with the OSB SIPs? It is recommended that with wood/OSB SIPs that you create a "cold roof" to prevent SIP rot. Building Science experts all agree that without a cold roof design, especially in a wet climate, you are asking for trouble in the long run.

Here is the article

Alton,
I was providing information about PU as a SIP core. The skin type could be anyone of many available in the SIP industry. You may have missed the point I was making, which is; if a PU core has a maximum thickness, then supplemental details must be used when meeting longer spans. These details often include a beefed-up spline connection that can create thermal bridges and a slower more difficult install. You are correct that any type of skin can be specified as thicker or made to have greater tensile strength and that will increase its transverse loading capacity. The thickest PU core available in the North American OSB SIP market is 7-1/4". However, most manufacturers stop at a 6-1/2" core. In metal skin PU panels, the thickest I've seen worldwide is 6".
Al

Boyne,
Here's my recommendation:
Have your SIP installer agree to meeting a level of air-tightness via a blower door test that demonstrates <1ach@50. Tie his final payment to passing the test. I'm sure he will be happy to tell you how experienced and capable he is at installation. Ask him to provide proof of his competency at the completion of his work.

A competent installer will have no problem in meeting that specification. In addition, a guarantee of air-tightness is your assurance of quality.
Your HERs rater also provides a level of quality assurance that keeps all your trades honest. He has the tools to inspect the envelope and identify where your SIP installer or other trades have allowed air leakage.

A trained and/or certified installer is your best assurance along with a HERs rater and his blower door test.

Al

Boyne,
Here's my recommendation:
Have your SIP installer agree to meeting a level of air-tightness via a blower door test that demonstrates <1ach@50. Tie his final payment to passing the test. I'm sure he will be happy to tell you how experienced and capable he is at installation. Ask him to provide proof of his competency at the completion of his work.

A competent installer will have no problem in meeting that specification. In addition, a guarantee of air-tightness is your assurance of quality.
Your HERs rater also provides a level of quality assurance that keeps all your trades honest. He has the tools to inspect the envelope and identify where your SIP installer or other trades have allowed air leakage.

A trained and/or certified installer is your best assurance along with a HERs rater and his blower door test.

Al

Lbear, You missed the most important part of that article. Joe clearly states that sealing the joint to make it air-tight is key. This is true in any type of panel regardless of skin or core type. An improperly sealed assembly allows vapor to reach a dew point and that puts moisture where you don't want it. That issue has nothing to due with skin type or even assembly type. A high performance assembly has an inherent reduced capacity to dry and back-ventilating (or as Joe says "a vented over-roof")(or as you incorrectly referred to as a "cold-roof")increases the assemblies capacity to dry which increases durability. This back-ventilation can be achieved with a self-ventilating cladding. OR as all questions about building science, one must first look at the climate zone and gauge the threat of cold dark and wet conditions that threaten durability. With proper detailing and installation, Any type of SIP can provide perfectly adequate service life in any climate. Al

OSB skins are not as good as metal.

Spoken like a true "Advanced Member" with no obvious bias.
All materials have there place along with pros and cons.
If you want to advance the SIP industry, you'd realize that promoting good design, sound engineering, and proper installation is far more constructive than vilifying one product type.

Surely you wouldn't interpret "not as good as" as vilifying a product type. But to advance the SIP industry, inherent flaws in one type of material should be recognized and acknowledged.

We've successfully installed PU SIPs for over 15 years. The one failure was a manufacturing problem from a company that went out of business (and took the equipment and principal to another business...beware). We have Thermocore panels on our own home and I agree with acobb's (hey, Al) that what's important is good design, sound engineering, and proper installation.

All kidding aside, until and unless the manufacturer stipulates that their polyurethane is being blown with a very low global warming potential (GWP) agent such as HFO1234yf, it's unlikely that the lifecycle atmospheric carbon savings from the higher R value will EVER make up for the impact of being blown with HFC245fa at about 1000x CO2 GWP.

There are at least two vendors of HFO1234yf based blowing agents for polyurethane under the trade names Solstice (Honeywall) and FEA-1100 (DuPont), but they have a truly tiny market share compared to HFC245fa (under a variety of trade names) foams. HFO1234yf has GWP of less than 5x CO2.

It's one thing to use modest amounts of closed cell spray polyurethane for air sealing & dew-point control in an assembly, but quite another to make it the primary insulation even at code-min R. Until they sort out the blowing agent issues, building with polyurethane SIPs is the chromatic opposite of "green".

EPS is all blown with pentane these days, with a GWP of about 7x CO2.

Dana1, Great info!

Another difference in PU foam vs EPS foam is their burning characteristics. The maximum working temperature of an EPS core panel is about 160 degrees Fahrenheit. EPS foam will melt at about 180 degrees Fahrenheit and burn at 212 degrees Fahrenheit. The maximum working temperature of a PU core panel is about 300 degrees Fahrenheit. PU foam will degrade at about 460 degrees Fahrenheit and burn at about 2200 degrees Fahrenheit. See video of PU SIP core burn demonstration at this link. http://www.youtube.com/watch?v=G9HlscKoJcY I have done this test myself with the same results.

Posted By JeffD on 15 Apr 2014 09:11 AM
Another difference in PU foam vs EPS foam is their burning characteristics. The maximum working temperature of an EPS core panel is about 160 degrees Fahrenheit. EPS foam will melt at about 180 degrees Fahrenheit and burn at 212 degrees Fahrenheit. The maximum working temperature of a PU core panel is about 300 degrees Fahrenheit. PU foam will degrade at about 460 degrees Fahrenheit and burn at about 2200 degrees Fahrenheit. See video of PU SIP core burn demonstration at this link. http://www.youtube.com/watch?v=G9HlscKoJcY I have done this test myself with the same results.

Jeff,
the numbers are a litte off
more like 167 long term service temperature and 180 maximum , in any event if it is 160 or 167 for a very short time you would be dead, as I recall you were living in an EPS SIP house too?

This is brought up a lot by PU SIP companies.

What's the hottest temperature that a Steel SIP roof will get with a standing seam metal roof on top of it? Can it see temps of 160F or higher?

What does one do with SCIPs, which also have an EPS core that is key to providing the wall and roof structural integrity? If the EPS foam melts, the structure fails.

Has a SIP home or roof with an EPS core ever caught on fire? If so, what were the results?

Posted By Lbear on 15 Apr 2014 11:24 PM
This is brought up a lot by PU SIP companies.

What's the hottest temperature that a Steel SIP roof will get with a standing seam metal roof on top of it? Can it see temps of 160F or higher?

What does one do with SCIPs, which also have an EPS core that is key to providing the wall and roof structural integrity? If the EPS foam melts, the structure fails.

Has a SIP home or roof with an EPS core ever caught on fire? If so, what were the results?

Lbear,
do the PU companies also bring up the fact that PU , off gasses, blisters and delaminates metal?
the only way for a fire to occur is for contents or electrical fires to happen.
I have heard of several cases of OSB SIP home content fires that have snuffed themselves out due to lack of oxygen

my thermal readings on Standing seam roofs have been 125 with black shingle roofs being 145